Ameloblastic Carcinoma

NORD gratefully acknowledges James M. Hall, DDS, Assistant Professor, Department of Oral and Maxillofacial Pathology, Tufts University School of Dental Medicine, for assistance in the preparation of this report.

Synonyms of Ameloblastic Carcinoma

No synonyms found

Subdivisions of Ameloblastic Carcinoma

No subdivisions found

General Discussion

Ameloblastic carcinoma is a rare malignant (cancerous) tumor that normally begins in the bones of the jaw. It is classified as an odontogenic tumor, meaning that it arises from the epithelium that forms the enamel of the teeth. The pattern of epithelial growth is similar to the developing tooth germ and distinctive enough to separate it from other epithelial malignances. Symptoms may include progressive pain and swelling of the jaw. Ameloblastic carcinoma may spread (metastasize) to affect other organs of the body.
Carcinoma refers to a malignancy that arises from epithelium. For instance carcinoma of the skin is termed 'squamous cell carcinoma' and carcinoma from glandular epithelium is termed 'adenocarcinoma'. The term "cancer" refers to a group of diseases characterized by abnormal, uncontrolled cellular growth that invades surrounding tissues and may spread (metastasize) to distant bodily tissues or organs via the bloodstream, the lymphatic system, or other means. Different forms of cancer, including odontogenic tumors, are classified based upon the cell type involved, the specific nature of the malignancy, and the disease's clinical course.

Signs & Symptoms

Some individuals with ameloblastic carcinoma may not experience any symptoms (asymptomatic). Symptoms that may occur include progressive pain and swelling of the jaw. Bleeding and headaches may also occur. Rare findings include the inability to open the mouth (trismus) or dysphonia, a voice disorder characterized by hoarseness, weakness, tingling or numbness (paresthesia), and, in rare cases, voice loss (my note: disruption of the voice because of laryngeal involvement (vocal cords) would be quite unusual but dysphagia, trouble eating, can be a problem if the tumor is large enough to cause obstruction or malocclusion). Nasal discharge and blockage of the nasal passages may occur if the tumor involves the sinuses of the maxilla. The size of the tumor may result in dental abnormalities such as causing the upper and lower teeth to fail to meet properly (malocclusion).

The lower jaw (mandible) is the most common site for the development of ameloblastic carcinoma. Less frequently, the upper jaw (maxilla) is the primary tumor site. In one reported case, the primary site was the anterior skull base.

Ameloblastic carcinomas are often aggressive and may spread (metastasize) to other areas of the body especially the lungs, potentially causing life-threatening complications. The bone, liver and brain are also common sites for metastasis. The most common course of the disease is persistent recurrence with local spread.

Causes

The exact cause of ameloblastic carcinoma is unknown. Most cases arise spontaneously without a previous history of cancer (de novo). Researchers speculate that genetic and immunologic abnormalities, environmental factors (e.g., exposure to ultraviolet rays, certain chemicals, ionizing radiation), diet, stress, and/or other factors may play contributing roles in causing specific types of cancer. Investigators are conducting ongoing basic research to learn more about the many factors that may result in cancer.

In individuals with cancer, malignancies may develop due to abnormal changes in the structure and orientation of certain cells known as oncogenes or tumor suppressor genes. Oncogenes control cell growth; tumor suppressor genes control cell division and ensure that cells die at the proper time. The specific cause of changes to these genes is unknown. However, current research suggests that abnormalities of DNA (deoxyribonucleic acid), which is the carrier of the body’s genetic code, are the underlying basis of cellular malignant transformation. These abnormal genetic changes may occur spontaneously for unknown reasons or, more rarely, may be inherited. In ameloblastic carcinoma, no genetic predisposition has been identified.

Ameloblastic carcinoma may develop from the epithelial tissue that remains after the development of the teeth and associated structures. In some cases, it results from malignant transformation of an existing ameloblastoma or a benign odontogenic cyst.

Affected Populations

Ameloblastic carcinoma affects males and females in equal numbers. They may affect individuals of any age including children, but the mean age of affected individuals is approximately 30 years old.

Related Disorders

Symptoms of the following disorders can be similar to those of ameloblastic carcinoma. Comparisons may be useful for a differential diagnosis.

Other odontogenic tumors and cysts must be differentiated from ameloblastic carcinoma especially ameloblastomas. Odontogenic tumors typically arise in the jaws, are slow growing and often have no apparent symptoms (asymptomatic). Pain is rarely associated with benign tumors or cysts, but common among malignant odontogenic tumors. Ameloblastic carcinoma must also be differentiated from carcinoma affecting the jaw that originates from a different primary site (such as metastases from lung cancer, breast cancer etc).

Ameloblastoma is a rare disorder of the jaw involving abnormal tissue growth. The resulting tumors or cysts are not malignant (benign), but the tissue growth may be aggressive in the involved area. On occasion, tissue near the jaws such as around the sinuses and the eye sockets may become involved as well. The tissues involved are most often those that give rise to the teeth so that ameloblastoma may cause facial distortion. Malignancy is uncommon as are metastases, but they do occur. (For more information on this disorder, choose “ameloblastoma” as your search term in the Rare Disease Database.)

Much confusion exists in the medical literature regarding the classification of malignant odontogenic tumors. An ameloblastoma is a slow-growing benign lesion that may spread to nearby tissues, but is not malignant. The term malignant ameloblastoma is used to denote an ameloblastoma that acts malignant (i.e., metastasizes) even though its cellular makeup does not indicate malignancy. Malignant ameloblastomas may metastasize to other organs, especially the lungs. Ameloblastic carcinomas are odontogenic tumors that display cellular characteristics of both an ameloblastoma and carcinoma. Ameloblastic carcinoma occurs more often than malignant ameloblastomas by a ration of 2:1.

Malignant ameloblastomas and ameloblastic carcinoma are classified as subtypes of primary intraosseous carcinoma type II, which refers to primary carcinomas of the jaw. PIOC type I refers to carcinoma arising from odontogenic cysts; PIOC type II refers to carcinoma arising from ameloblastomas or containing cellular elements of an ameloblastoma; and PIOC type III refers to carcinoma of the jaws without identifiable cause (de novo).

Diagnosis

A diagnosis of ameloblastic carcinoma is made based upon a thorough clinical evaluation, a detailed patient history, and microscopic examination of the tumor. Most cases are found incidentally. One procedure is known as fine needle aspiration, in which a thin, hollow needle is passed though the skin and inserted into the nodule or mass to withdraw small samples of tissue for study.

In addition to biopsies, various x-ray techniques may be used to help evaluate the size, placement, and extension of the tumor and to serve as an aid for future surgical procedures. Such imaging techniques may include computerized tomography (CT) scanning and magnetic resonance imaging (MRI). During CT scanning, a computer and x-rays are used to create a film showing cross-sectional images of certain tissue structures. An MRI uses a magnetic field and radio waves to produce cross-sectional images of particular organs and bodily tissues. Laboratory tests and specialized imaging tests may also be conducted to determine possible infiltration of regional lymph nodes and the presence of distant metastases.

Standard Therapies

Treatment
The therapeutic management of individuals with ameloblastic carcinomas may require the coordinated efforts of a team of medical professionals, such as physicians who specialize in the diagnosis and treatment of cancer (medical oncologists), specialists in the use of radiation to treat cancer (radiation oncologists), dental specialists, surgeons, oncology nurses, and other specialists.

Specific therapeutic procedures and interventions may vary, depending upon numerous factors, such as primary tumor location, extent of the primary tumor (stage), and degree of malignancy (grade); whether the tumor has spread to lymph nodes or distant sites; individual’s age and general health; and/or other elements. Decisions concerning the use of particular interventions should be made by physicians and other members of the health care team in careful consultation with the patient, based upon the specifics of his or her case; a thorough discussion of the potential benefits and risks; patient preference; and other appropriate factors.

Wide surgical excision provides the best chance of controlling the tumor. Adjunctive radiation may be used however radiation treatment has not been effective as a primary form of therapy. Radiation therapy may also be performed before surgery to decrease tumor size. Recurrence of ameloblastic carcinoma after surgical removal may occur and may involve various organs in the body with or without recurrence in the jaw. Most commonly recurrences are seen in the same area as the original tumor. Recurrence may occur within a year of surgery or several years later. Because of the risk of recurrence, life-long periodic physical examinations are necessary.

Chemotherapy has not proven effective in treating individuals with ameloblastic carcinoma and is most often used to try and control wide spread metastases. Developing the optimal treatment for individuals with ameloblastic carcinoma has been hindered because of the relatively few identified cases.

Investigational Therapies

Information on current clinical trials is posted on the Internet at www.clinicaltrials.gov. All studies receiving U.S. government funding, and some supported by private industry, are posted on this government web site.

For information about clinical trials being conducted at the NIH Clinical Center in Bethesda, MD, contact the NIH Patient Recruitment Office:

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If you are seeking information about a rare disease that is not in this database, we would suggest contacting the Genetic and Rare Diseases Information Center (GARD) at the National Institutes of Health. NIH has the most complete database of rare diseases in the U.S.

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